This invention relates to a ring binder mechanism for retaining loose-leaf pages, and in particular to an improved mechanism for reducing snapping motion of ring members as they close, for securely locking closed ring members together, and for preventing misalignment of closed ring members.
A ring binder mechanism retains loose-leaf pages, such as hole-punched pages, in a file or notebook. It has rings for retaining the pages. The rings may be selectively opened to add or remove pages to the rings or closed to retain pages on the rings while allowing the pages to move along the rings. Ring members of each ring mount on two adjacent hinge plates. The hinge plates join together about a pivot axis for pivoting movement within an elongate housing. The housing holds the hinge plates so they may pivot relative to the housing and move the ring members between an open position and a closed position.
The undeformed housing is narrower than the joined hinge plates when the hinge plates are in a coplanar position (180 degrees). So as the hinge plates pivot through this position, they deform the resilient housing and cause a spring force in the housing that urges the hinge plates to pivot away from the coplanar position and move the ring members to either their open or closed position. This spring force is generally large so that the housing can resist unwanted hinge plate movement through the co-planar position (e.g., hold the hinge plates against movement tending to open closed ring members).
However, the large housing spring force causes the hinge plates to pass through the co-planar position with a strong snapping movement. As a result, closing ring members may snap together rapidly and with a force that might cause fingers to be pinched between the ring members. The large spring force can also make it difficult to move the hinge plates through the co-planar position so that it is difficult to open and close the ring members. In addition, the housing may begin to permanently deform over time because of repeated movement of the hinge plates through their co-planar position. This may reduce the housing's ability to resist unwanted hinge plate movement.
Some ring mechanisms include locking structure that positively blocks the pivoting movement of the hinge plates when the ring members are closed. This allows the housing spring force to be reduced while still securely locking the closed ring members together. But the paired ring members of these ring mechanisms often have free ends with tip formations that do not always exactly align when the ring members are closed. Misalignment of the ring members in directions transverse to longitudinal centerlines of the ring members is common. Moreover, even if alignment is initially perfect upon closure, the free ends may still be able to move relative to each other after the ring members close. While the engagement of the ring member free ends may be capable of resisting displacement in one direction, most cannot resist displacement in a second, perpendicular direction. For example, the ring member free ends are often shaped to resist relative displacement toward and away from the longitudinal axis of the ring binder mechanism, but provide no resistance to relative movement in directions along the length of the ring binder mechanism. Accordingly, pages bound by these known mechanisms may not smoothly move from one ring member to the other and may be torn.
Accordingly, there is a need for a ring binder mechanism that positively locks to hold closed ring members together and that has paired ring members with free end formations that prevent misalignment of the closed ring members in all directions transverse to longitudinal centerlines of the ring members.